Fair Value - Summary of Quantitative Fair Value Measurements for Level 3 (Detail) - Fair Value, Inputs, Level 3 $ in Thousands	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Impaired loans, net	$ 4,700	$ 3,491
Other real estate owned, net	$ 3,597	$ 4,284
Impaired Loans | Discounted Appraised Value | Lack of Marketability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Impaired loans	100
Minimum | Impaired Loans | Discounted Appraised Value | Selling Cost
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Impaired loans	15	6
Minimum | Impaired Loans | Discounted Appraised Value | Lack of Marketability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Impaired loans		50
Minimum | Impaired Loans | Discounted Cash Flows | Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Impaired loans	5	5
Minimum | Other Real Estate Owned | Discounted Appraised Value | Selling Cost
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Other real estate owned	5	3
Minimum | Other Real Estate Owned | Discounted Appraised Value | Lack of Marketability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Other real estate owned	9	10
Maximum | Impaired Loans | Discounted Appraised Value | Selling Cost
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Impaired loans	20	20
Maximum | Impaired Loans | Discounted Appraised Value | Lack of Marketability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Impaired loans		90
Maximum | Impaired Loans | Discounted Cash Flows | Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Impaired loans	7	6
Maximum | Other Real Estate Owned | Discounted Appraised Value | Selling Cost
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Other real estate owned	19	13
Maximum | Other Real Estate Owned | Discounted Appraised Value | Lack of Marketability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Other real estate owned	100	100
Weighted Average | Impaired Loans | Discounted Appraised Value | Selling Cost
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Impaired loans	16	16
Weighted Average | Impaired Loans | Discounted Appraised Value | Lack of Marketability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Impaired loans	100	65
Weighted Average | Impaired Loans | Discounted Cash Flows | Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Impaired loans	6	6
Weighted Average | Other Real Estate Owned | Discounted Appraised Value | Selling Cost
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Other real estate owned	8	8
Weighted Average | Other Real Estate Owned | Discounted Appraised Value | Lack of Marketability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Unobservable Input, Other real estate owned	28	16